We built browser-metro, a Metro-like bundler that runs entirely in a Web Worker. It supports full HMR with React Refresh, Expo Router with file-based routing, and on-demand npm package resolution via an ESM server. API routes run in-browser through fetch interception — no server or service worker needed. Unlike Expo Snack (server-side bundling) or CodeSandbox, everything here happens client-side. Currently web-preview only; native device preview is on the roadmap.

Open source (MIT): https://github.com/RapidNative/reactnative-run